Design issue - calculate the power requirement for 8 kn jet

[Tealc]

Hello!
I'm trying to design a 75 metres long, 2.5 metres draught self-propelled barge for my graduation paper (which is due in june ), and i'm to utilize as propulsion a jet drive. As the barge should be at around 1500 tonnes of displacement and have an operating speed of at least 8 kn, I do believe that I need something like a traktor type jet -- although I've recently found a so called pump jet system from Schottel (see the link below) which seems more suitable for my application.
http://www.schottel.de/eng/r_produkt...uebersicht.htm

The problem that I have is that I do not seem to find a way to calculate the power requirement for the jet engine. All I found are ways of calculating the power rating for planning or semi-planning type hulls and for speeds of more than 20 kn (which for my ship would be too much, as it is intended to operate the Danube river).

Can anyone help me, please?

[Guillermo]

For a different approach, you may also try:
Hydrodynamic Flushing:
http://www.tyvik.com/index.html
Whale Tail Wheel:
http://www.marinetalk.com/articles-m...on-74828T.html
http://www.nap.edu/nap-cgi/skimit.cg...1&chap=946-958

[Tealc]

Thanks for the tips, but now I've advanced with the current design and it's a little late to change it....I mean I'm almost finished with the drawings and I'm only to write down the theoretical model. I really would like to know if anyone had heard about a way to calculate engine power for my current design.

[Tad]

Hi Teal,

I believe the subject is covered in the most recent edition of Principals of Naval Architecture, published by SNAME in the US. Your library may be able to obtain a copy.

The best coverage I know of is a paper, Marine Waterjet Propulsion, by John Allison, also published by SNAME in about 1993. This gives a complete procedure for calculation of waterjet thrust.

Tad

[yipster]

forgive my ignorance but i did not know jet drive propulsion was economical at slow speeds
a while back i saw pics of a cat ferry having his big jets taken out by a small U shaped service boat that fitted in and under
maybe thats common practise but it looked smart to me

[Tealc]

indeed as I saw myself the jet drive propulsion isn't recomended for slow speeds (less than 20 knotts)....however recent development of the water jet engine has produced the 360 degrees thruster which is already in use in some similar applications (see the link I gave in the original thread), but the real problem is the lack of information covering the subject. I've already contacted some of the producers of this kind of engine (via e-mail of course) but I haven't as yet received some (intelligent) answer. The solution of the water jet engine seems to be the best (it will fit rather nicely under the hull and the are no additional appendages), as the barge is intended to be a part of a self-propelled train of barges....

[yipster]

sorry dint check threat and now i did this is the jet you mean right?
schottel should have all you want to know i would think
no taking that out at the waterline i suppose but me updated

[Tealc]

actually this is what i have in mind...on the Danube the are some situations when the water depth may be as low as 1,5 metres (in the summer mostly). Of course that in this case the vessel should remain safely in port, but with a design depth of 2,5 m the vessel can safely navigate waters 2,8-3 m in depth...and the type of engine that i'm considering also permits a higher degree of manoeuvrability when we have a train of barges -- and most of the time that's the way the ships are designed to navigate - it's a lot more cost efective!

[yipster]

tree times lazy, dont make it a fourth by telling me its another nozzle
btw dont think ive seen this thruster before, so thanks for the info Tealc

[yipster]

been thinking about this one, keep me updated on specs please

[Tealc]

if i get any replies from scottel or if i find out more details, i will keep you updated......

[Guillermo]

Originally Posted by Tealc

indeed as I saw myself the jet drive propulsion isn't recomended for slow speeds (less than 20 knotts)....

This guys wouldn't agree...http://www.marinejet.com/

[Tealc]

i already said that there are some jet's that can fulfill the taskin hand.......unfortunately there aren't enough informations about them...like thrust to power ratios or something similar....that normally wouldn't be a problem, if one is not sure about the power requirement, one can simply choose the biggest jet and that will work for sure....my problem is that the vessel will be a full electric one, that is even the jet will be powered by the way of an electric motor and this is where i have my problem: what power do i need to get installed aboard?

[Guillermo]

I suggest you to ask Marinejets for advice.

[Lion_Power]

Would you please provide me with Ship Construction Manual in PDF Format..

I'll appriciate your fruitfull response.